FR2840747A1 - Biometric access authentication method wherein each time access is required a fingerprint sample is compared with a stored encrypted reference with the new fingerprint sample forming a new reference after a positive comparison - Google Patents

Abstract

Method for checking an electronic signature in the form of a biometric fingerprint, whereby a fingerprint (EB) is recorded and analyzed to form a sample (ECH). The sample is compared (204) with a reference value the has been decrypted using a key requested from a server. If the comparison is positive access is grated. The sample is then used to form a new encryption key, which is stored in the server together with the new encrypted reference value. The new encrypted reference is also stored locally.

Description

saturable type without electrode.

  The present invention relates to an electronic signature of the user of a computer for controlling the authorization of access of a certain user or group of user to a computer, in particular for carrying out transactions, the electronic signature being the fingerprint. s user and computer biometric, equipped with a sensor

  biometric fingerprints, is linked to a server.

Prior art

  There are many electronic signature systems.

  The problem of all existing systems lies in the greater or lesser security of these systems, especially since they must take into account the regulations concerning the protection of confidential information.

  relating to personnel which must be contained in files.

  The purpose of the present invention is to develop an electronic signature system, offering very high security guarantees for access to a computer of an authorized person in order to execute transactions and which is also protected against all intervention. hacking, likely to collect confidential information

  during the execution of the transaction through a network.

  Object of the invention o To this end, the invention relates to an electronic signature of the type defined above, characterized in that A) at the first protected use of the computer: - the user's biometric fingerprint is entered authorized with the biometric sensor associated with the computer, - we assign an identification number to the user, - we analyze the biometric fingerprint to determine its particularities (minutiae, points X, Y) and their relative position in a system coordinates to form a reference, - we form an encryption key by applying an encryption program to the reference, - we encrypt the reference with the encryption key thus obtained to form the encrypted reference, - we delete the fingerprint entered and the reference, - we locally store the encrypted reference with the identification number, we send the key to the servour with the identification number, - we delete the key in the computer, B) during a subsequent access to l computer: - we know if the biometric fingerprint, - we analyze the fingerprint and we form a sample using the analysis program, - we send a request for a key with the identification number to the server, which returns the key associated with the number identification, - we encrypt the encrypted reference in gi stree lo cally with the key, - we compare the sample to the decrypted reference: * if the comparison is positive, the access authorization is accor io of and we forms a new encryption key transmitted to the server under the same identification number to replace the old key and with this new key, the sample is encrypted which becomes an encrypted reference replaced by the previous reference, * if the comparison is negative , the authorization of access is refused. The electronic signature according to the invention has the advantage of respecting the confidential nature of the information relating to the authorized person, that is to say his biometric fingerprint since this information is not kept in the memory of the computer, or somewhere else. Only wind kept on the one hand, the encryption key established from the biometric fingerprint and this encryption key is not registered in the computer whose access must be authorized but in a servour and on the other hand, the encrypted reference saved locally either in: 5 the computer or indirectly on a medium laughable by

  the computer using peripheral equipment.

  However, the encryption key cannot be used alone. There is

  even the encrypted reference which cannot be used if it is not decrypted.

  Information security is therefore ensured by recording it in the form of additional information (key, encrypted reference) in places

  different and unusable in isolation.

  The encryption key is unique because it was obtained from the biometric fingerprint or more precisely from the trace collected by a biometric fingerprint sensor. This trace, reproduces the particulars of the imprints, for example in the case of a fingerprint the arcs, loops, volutes ..., forming the minutiae, that is to say the particular points of the footprint such as the points called points X and Y corresponding to the crossing or to the junction of ribs of the footprint

  digitalis. Because even if the particular points of the wind imprint remain unchanged

  gees, their relative position relative to the sensor can vary according to the part of the user's finger which will give the imprint and is never exactly the same. Likewise, the force with which the user presses his finger and more or less crushes it, modifies the trace of the fingerprint which varies from one capture operation to another so that the relative position of the minutiae is different. Indeed depending on the more or less significant crushing of the finger, the relative spacing of the minutiae can be modified

  in the width, in the length or in a combined way.

  o Thus after having compared this new fingerprint in its analyzed form, called sample to the reference decrypted with the encryption key returned by the server and applied to the encrypted reference recorded locally in the computer or on a medium laughable by it, the program checks if the new fingerprint can be considered identical to the old one. This new fingerprint will also be used to form an encryption key integrating random elements and this encryption key will be different from the previous encryption key. This new encryption key will be sent to the server without leaving a trace on the computer, to be kept there until the next access request. At the same time, this new encryption key will have been used to encrypt the sample accepted as

  new biometric fingerprint reference which will be registered locally

  Also as an encrypted reference with the identification number. All other information and data such as the fingerprint entered, the reference (not encrypted), the encryption key will be deleted. At the same time, this new encryption key will have been used to encrypt the accepted sample.

  as a new reference for the biometric print and which will be registered

  be locally as an encrypted reference with the identification number, all other information and data such as the fingerprint entered, the

  so reference (not encrypted), the encryption key will be deleted from the computer.

  Thus each time an authorization request is made for access to the computer, a new encryption key is formed for the next access operation, without this encryption key being able to be deduced in any way from the previous key. . The encryption key remains saved

  s5 tree in the server until it is replaced by a new key.

  We thus considerably increase the security of the signature since even a hacking of the computer only allows to obtain sometimes only the key used and which cannot serve a second time. According to another interesting characteristic, we locally store the encrypted reference in the computer or in a lisi support

  directly by computer (smart card, USB key, IBUTION).

  The information to be stored may be compressed before saving

  istration; they will then be decompressed during reading.

  According to another advantageous characteristic, in the case of several users authorized to access the computer, each is identified by an identification number associated respectively with the keys of

  encryption and successive encrypted references of each user.

  Thus, according to the above procedure, the authorized user (s) of the same computer will not have to know their number

  identification which also increases security.

  According to another characteristic, the identification numbers NI (i) are stored in the computer and, when accessed by one of the authorized users, after entering their bio-metric footprint EB, the computer successively uses the different NI identification numbers (i) to request each time the encryption key associated with the server; perform the checks with this encryption key (decryption, comparison of the encrypted reference and the sample, formation of a new encryption key and a new encrypted reference and their recording, deletion of the old references, old keys of the reference used for the new encryption) or definitively refuse access

  2s if the different comparisons were all negative.

  Thus, according to the above procedure, the authorized user (s) of the same computer will not have to know their number

  identification, which also increases security.

  Advantageously, at the time of the access request, the computer creates a token which goes around the network so as not to allow

than a transaction.

  The use of a modified token at each operation allows

  increase the security of the electronic signature.

  This token is a random number identifying the transaction

and changes with each operation.

  Drawings The present invention will be described below in more detail with the aid of the annexed drawings in which: - Figure 1 shows a diagram of the installation according to the invention, - Figure 2 shows a simplified flowchart of the establishment of the electronic signature control means according to the invention, - Figure 3 is a simplified flowchart of the control procedure

  s a request for access to the protected computer.

Description of embodiments

  According to figure 1, the invention relates to a method for checking an electronic signature intended to allow an authorized user to access a computer 1 to carry out transactions which do not cease protection, such as for example commercial transactions.

  companies, sending a debit order or an amount of money.

  For this, according to the invention, access to the computer 1 is given only after verification of a biometric fingerprint of the authorized user. The control is preceded by a first step consisting of recording on the computer, the electronic signature of the user (s) who will be authorized. This electronic signature is associated with a biometric fingerprint of each user, for example his fingerprint. It is only after this first registration that the user (s) can request access by providing each time their biometric fingerprint will be established which will be checked at the same time.

  new control elements (encryption key, encrypted reference).

  The following description will be made with example of

l fingerprint.

  FIG. 1 shows diagrammatically the means of control: 5 of an electronic signature associated with a computer 1. The computer 1 is equipped with a biometric fingerprint sensor 2 such as a fingerprint sensor. It processes the fingerprint thus captured using a PRA analysis program to deduce encrypted information from it using a PRC encryption program. The information will make it possible to control the authorization of access of a user to the PC to carry out the transactions as indicated above. The system also includes a server S to which the computer accesses via a network R. This server receives the encryption key established by the PRC program from information linked to the first entry of the biometric fingerprint. The server provides this information in return to the request from computer 1 and after the access authorization has been checked, the user then authorized can carry out transactions with a supplier Fi via the network R. different operations will be described below in more detail using the flowcharts of Figures 2 and 3. These operations of control of user identity are carried out in two stages, a preliminary stage consists in registering a user authorizes and the following stages during which

  the user requests access to the computer.

  The preliminary step of registering the user or users is represented diagrammatically in the form of an ordino 10 gram in FIG. 2 and the operations for controlling authorization of access are represented diagrammatically by the flow diagram of the figure 3,

  supplemented by part of the flowchart in Figure 2.

  According to FIG. 2, during the preliminary step an authorized user is recorded by first taking his biometric impression EB (100) by the sensor 2. Then, the impression thus captured and analyzed (101 ) with a PRA analysis program (102). This analysis consists in determining the peculiarities of the trace of the EB biometric imprint. In the case of a fingerprint, examined more particularly here, this analysis consists in determining the minutiae of the trace o (fingerprint), that is to say the particular points of the fingerprint, such as

  points X, Y and their relative coordinates.

  It should be noted here that a distinction must be made between the biometric fingerprint properly cited such as the relatively abstract fingerprint and the trace of this fingerprint on the sensor. This trace which is on the contact surface between the finger and the sensor. This trace represents only part of the totality of the fingerprint. Wile depends on the part of the finger which is applied to the sensor and the pressure exerted on the finger, i.e. the crushing of the contact surface between the finger and

the sensor.

  This means that the trace of the biometric imprint (global imprint) is never the same for the same person because the particular points or minutiae contained in the trace can differ depending on the surface applied. Their relative coordinates may also vary. These relatively small wind variations but sufficient to be distinguished by the analysis program and used in the conditions

which will be seen later.

  The result of this analysis is to obtain a set of data called "RF reference". The first reference, that is to say that associated with the analysis of the first impression of the user which will be authorized, is called RF (0). The following references associated with each new fingerprinting of this same user authorized, will be called RF (1), RF (n), RF (n + l), At the same time as the PRA program analyzes the EB footprint of user Ui, the computer establishes (103) an identification number

  NI (i) assigns this user Ui.

  Then, using a PRC program, the computer trains

  (104) an encryption key CL (0) (105) from the reference RF (0).

  o Using the encryption key CL (0) and the RF reference (0), the computer encrypts the reference, that is to say, forms an encrypted reference

RFC (0) (106)

  This RF encrypted reference (0) is stored locally (107) either in the computer or on a medium accessible to the computer such

  than a smart card that gets into a reader linked to the computer.

  At the same time as the encrypted reference RC (0) is saved tree, the key CL (0) is sent (108) to the server S then the key CL (0) is erased

this (109) of the computer.

  Likewise, the RF reference (0) is deleted (110).

  o The encryption key CL (0) is sent to the servour together with the identification number NI (i). This number is also associated

  cie to the locally saved RFC (0) encrypted reference.

  These operations complete (113) this preliminary step.

  The computer is now ready to receive a request: 5 accesses by a user and can check if this user is authorized to

access the computer.

  The flow of these operations is represented by the flowchart in Figure 3 also using steps from the flowchart in Figure 2. For this reason, the designations indices were double; for example, the index O for the preliminary operation is the index 1 for the next operation and so on (n) and (n + l) During a first step (200), the user does take its biometric print by sensor 2. This print is analyzed by the computer (201) which forms an ECH sample. This sample s5 corresponds to what, by the analysis operation (101) of the preliminary step,

gave the reference.

  The ECH sample contains the particular points of

  the biometric footprint and their positioning.

  The computer also requests (202) the key from the server S

  by sending him a request with the identification number NI (i).

  It is assumed here that there is only one identification number available on the computer which processes the access request. The server S

  s is answered by sending the key CL (0) associated with the identification number NI (i).

  This key CL (0) is used by the computer and the program

  PRC encryption to decrypt (203) the RFC encrypted reference (0) saved

  tree in the computer and associated with the NI (i) identification number.

  Next, the computer compares (204) the ECH sample and the decrypted RF reference (0). This comparison (204) of the two sets of information is made according to criteria depending on the nature of

  the biometric print. We consider that the information is equ * a-

  slow if the sample, that is to say the particular points of the new fingerprint captured, is sufficiently close to the particular points of the

RF decrypted reference (0).

  If yes (205), access is allowed (206) to the computer. At the same time as access is authorized, the computer forms (207) a new encryption key CL (1) from the sample ECH with the program PRC. In this operation, the sample is considered

  o as the reference of the fingerprint entered in point 200.

  We thus obtain an encryption key CL (l, n + l). This key of

  CL encryption (l, n + l) is then used in a manner analogous to what has been

  written about figure 2 for the preliminary step, to encrypt the refe-

  rence (old sample), ie the RF reference (1, n + l). The

  : 5 reference encrypted with the encryption key gives the encrypted sample, that is

  ie the new RFC encrypted reference (l, n + l) which is then stored

  locally. The new CL key (l, n + l) is sent to the server under the number

  NI (i) identification mero, which remains unchanged. The new reference cryp-

  tee RFC (l, n + l) is saved locally under the number

o NI (i) identification.

  As before, the encryption key is deleted from

  the computer as well as the sample and the reference, senle restart enre-

  locally store the RFC encrypted reference (l, n + l) and its number

NI (i) identification.

  s The new CL encryption key (l, n + l) is sent to the server to replace the previous CL (0) encryption key associated with the same

NI (i) identification number.

  For the following operations, when the user wishes to access the computer again after the end of the previous session, he

  re-enter his biometric print (200). This is analyzed

  see (201) to give an ECH sample and at the same time a request for an encryption key is sent to the server with the NI identification number (i). After reception of the encryption key CL (1) from the server S. the computer decrypts (203) the RFC reference (1) recorded locally under the identification number NI (i). This RF decrypted reference (1) is then used to

  be compared (204) to the ECH sample.

  lO If the response is positive (205), access is authorized (206) and a new encryption key CL (2, n + 2) is formed (207). This key is used to encrypt the ECH sample, ie the new reference which becomes the RFC encrypted reference (2, n + 2) This encrypted reference is always saved locally under the identification number NI (i) and the other information is again erased from the computer at the same time as the new key CL (1) is sent to the server under the number

d / NI identification (i).

  The operations are repeated as already described using FIG. 2. If the comparison (204) gives a negative result

(209), access is prohibited (210).

  With each new access request, the operations described

  above repeat themselves. This can be seen in the description above in

  replacing indices 1, 2 by n, n + l.

  In the case where several users are authorized for the same computer, the situation is very similar. Each user registers their identity during a preliminary step, that is to say that they enter their biometric fingerprint to obtain an NI identification number (i), a first encryption key and a first refe

  rence encrypted then the operations are repeated.

  Each user is necessarily associated with an encryption key and an encrypted reference, different both because the biometric fingerprint is different and because with each new request for authorized access, the system forms a new encryption key and

a new encrypted reference.

  According to a characteristic of the invention, the identification numbers NI (i) are not supplied to the users but remain in registers as they are on the computer without being associated directly with a

  user, that is, has a user name.

  During a request for access by a user Ui, the latter takes his biometric print (200) then the computer requests the key

  encryption to the server. For this, the computer uses for example the pre-

  mier NI identification number (1). The server hands over the encryption key associated with this identification number. Then the computer compares the sample and the decrypted reference associated with this identification number

  NI (1). If the comparison shows that there is identity (205), access is authorized.

  is; a new encryption key and a new encrypted reference wind formed under the conditions already described and they replace the old ones

o information.

  If the comparison gives a negative result (209), access is not automatically prohibited but the operation resumes (211) with a

  another NI (i) identification number, for example the following NI (2) number.

  The key request, the comparison with the sample and the following operations

  s vantes wind repeated with this new key and the new reference de-

  encrypted associated with this NI identification number (2). If the comparison is

  positive, operations stop under the conditions already indicated, that is

  to say that access is authorized; a new encryption key and a new

  velle reference encrypted wind formed and saved one in the server, or the other locally. If the comparison response (204) is negative (209), the operation is repeated with another NI identification number (i), for

  example the following number NJ (3) in an order which does not matter.

  The operations are repeated until a positive response is obtained (205) or in the event of a negative response for all the numbers.

  s NI (i) identification and associated encryption keys, access is inter-

says (210).

  The operations described above can be protected by a token issued at each access request and specific to each foist This token is formed in the computer and in the server according to

  so an identical algorithm to allow the recognition of the token.

Claims (4)

R E V E N D I C A T I O N S   1) Method for controlling the electronic signature in the form of a biometric fingerprint of a computer user to verify his authorization of access, in particular to carry out transactions with this computer, the latter equipped with a sensor of biometric fingerprints being linked to a server, process characterized in that A) at the first protected use of the computer: - the biometric fingerprint EB of the authorized user is entered with o the biometric sensor (2) associated with the computer, - we assign an identification number NI (i) to the user, - we analyze the biometric fingerprint EB to determine its particularities (minutiae, points X, Y) and their relative position in a system of coordinates to form an RF reference (0), S - we form an encryption key CL (0) by applying a PCR encryption program to the RF reference (0), - we encrypt the RF reference (0) with the CL (0) encryption thus obtained to form the RFC (0) encrypted reference, - we delete the fingerprint entered EB and the reference RF (0), - we locally store the encrypted reference RFC (0) with the identification number NI (i), - we send the key CL (0) to the server with the number d / identification NI (i), - we delete the key CL (O) in the computer, B) during a following access to the computer: - we enter the biometric fingerprint EB, - we analyze the EB footprint and we form a sample ECH using the PRA analysis program, - we send a key request with the identification number NI (i) o to the servour, which returns the key CL (0) associated with the NI identification number (i), - we encrypt the encrypted RFC reference (0) stored locally with the key CL (0), - we compare the ECH sample to the decrypted reference RF (0): * if the comparison is positive, the authorization of access is granted and a new encryption key CL (1, n + 1) is transmitted transmitted to the server under the same identification number NI (i) replacing the old key CL (O , n) and with this new key CL (1 , n + l), we encrypt the sample ECH which comes from an encrypted reference RFC (1, n + l) replacing the previous reference RF (O, n), * if the comparison is negative, the authorization of access is refused. 2) Control method according to claim 1, characterized in that the encrypted reference RFC (O, n) is stored locally in the computer or   o in a medium laughable directly by the computer (smart card, ...).   3) Control method according to claim 1, characterized in that in the case of several users (Ui) authorized to access the computer,   s each is identified by an associated NI (i) identification number   to CL (n, i) encryption keys and RFC (n, i) encrypted references   of each user Ui.   4) Control method according to claim 3, characterized in that the identification numbers NI (i) are recorded in the computer and, during   access by one of the authorized users, after entering their em-   biometric EB, the computer successively uses the different identification numbers NI (i) to request each time the 2s-stage encryption key associated with the servour; perform the checks with this encryption key (decryption, comparison of the encrypted reference and the sample, formation of a new key   encryption and a new encrypted reference and their registration, e-   facade of the old references, old keys of the reference having been used for the new encryption) or definitively refuse access if the different comparisons have all been negative. ) Control method according to claim 1, 3s characterized in that at the time of the identification request, the computer creates a token which   goes around the network to allow only one transaction.   6) Method of control according to claim 5, characterized in that the token is a random number identifying the transaction and modifies each operation.